1. Field of the Invention
The present invention relates to a microscanner and optical equipment having the same.
2. Description of Related Art
Conventionally, various types of small optical scanners (microscanners) are developed, which utilize MEMS (Micro Electro Mechanical Systems) technology. For example, a first patent document (JP-A-2005-128147, paragraph 0024 and the like) discloses an optical scanner LS′ as shown in FIG. 16, which includes a mirror part MR′ for scanning, a torsion bar TB′ for supporting the mirror part MR′, and a diaphragm 101 that is connected to the mirror part MR′.
The optical scanner LS′ has a structure for tilting the mirror part MR′ as much as possible, in which a drive frequency of piezoelectric actuators 102 on the diaphragm 101 is the same as a mechanical resonance frequency of the mirror part MR′ including the torsion bar TB′. According to this structure, the mirror part MR′ can be vibrated and tilted relatively largely even if the piezoelectric actuator 102 is driven by a low voltage.
However, a tip part 103 of the diaphragm 101 connected to the mirror part MR′ is hardly deformed in torsion. Therefore, a force generated in the diaphragm 101 hardly exerts on the mirror part MR′ as a rotation torque. Thus, it is difficult to say that the mirror part MR′ is sufficiently tilted.
Here, there may be another structure of the optical scanner LS′ in which the tip part 103 is not connected with the mirror part MR′. For example, there is a structure of the optical scanner LS′ as shown in FIG. 17. This optical scanner LS′ includes the mirror part MR′, a holding parts HD′ that can be deformed by the piezoelectric elements PE′, and a main axis parts MA′ connecting the mirror part MR′ with the holding parts HD′.
This optical scanner LS′ rotates the mirror part MR′ in the normal or the reverse directions with respect to an X′ direction (in a P′ direction or an R′ direction) corresponding to deformation in flexion of the holding parts HD′. The holding parts HD′ that is deformed in flexion on the tilting operation of the mirror part MR′ as described above is shown in FIGS. 18A and 18B. FIG. 18A shows a cross section cut along the line a-a′ in FIG. 17 in case of the normal rotation while FIG. 18B shows another cross section in case of the reverse rotation.
For convenience of description, an axial direction of the main axis parts MA′ is referred to as the X′ direction (or an X′ axis), an extending direction of the holding parts HD′ that is perpendicular to the X′ direction is referred to as a Y′ direction, and a direction that is perpendicular to the X′ direction and to the Y′ direction is referred to as a Z′ direction. In addition, the upper side of FIG. 17 is referred to as a plus side in the Y′ direction (Y′(+)) while the lower side opposite to the plus side is referred to as a minus side in the Y′ direction (Y′(−)). Furthermore, a front side of the paper of FIG. 17 is referred to as a plus side in the Z′ direction (Z′(+)) while a back side opposite to the plus side is referred to as a minus side in the Z′ direction (Z′(−)).
Furthermore, only one of the two holding parts HD′ (a first holding part HD1′ and a second holding part HD2′) is described below. When the first holding part HD1′ is going to rotate the mirror part MR′ in the normal or the reverse direction, the second holding part HD2′ is also going to rotate the mirror part MR′ in the normal or the reverse direction in the same manner.
When the mirror part MR′ rotates normally as shown in FIG. 18A, a piezoelectric body PB′ of the piezoelectric element PE′ on the Y′(+) side expands so that the main axis parts MA′ side of the holding parts HD′ on the Y′(+) side droops toward the Z(−) side. At the same time, a piezoelectric body PB′ of the piezoelectric element PE′ on the Y′(−) side contracts so that the main axis parts MA′ side of the holding parts HD′ on the Y′(−) side rises toward the Z(+) side. Then, the holding parts HD′ is deformed like a wave, and the main axis parts MA′ is tilted in the normal direction responding to the deformation.
On the contrary, when the mirror part MR′ rotates reversely as shown in FIG. 18B, the piezoelectric body PB of the piezoelectric element PE′ on the Y′(+) side contracts so that the main axis parts MA′ side of the holding parts HD′ on the Y′(+) side rises toward the Z(+) side. At the same time, the piezoelectric body PB of the piezoelectric element PE′ on the Y′(−) side expands so that the main axis parts MA′ side of the holding parts HD′ on the Y′(−) side droops toward the Z(−) side. Then, the holding parts HD′ is deformed like a wave opposite to FIG. 18A, and the main axis parts MA′ is tilted in the reverse direction responding to the deformation.
However, the plate-like holding parts HD′ having a uniform thickness possesses relatively high stiffness and is hardly deformed in flexion. In addition, since the deformed part of the holding parts HD′ (a bent part 107) is generated at a position relatively far from the X′ axis, it is difficult to tilt a part of the holding parts HD′ connected to the main axis parts MA′. Therefore, this optical scanner LS′ is difficult to increase a tilt angle θ′.
Furthermore, there is a method of making the holding parts HD′ be deformed in flexion easily by forming a part (the bent part 107) thinner than other parts of the holding parts HD′. In this case, an etching process may be used for example, but it is very difficult to control the thickness of the holding parts HD′ accurately by the etching process because it is affected by various process conditions.
It is also possible to make the substrate of the holding parts HD′ as a SOI (Silicon on Insulator) substrate for accurate etching. However, it will increase cost of the optical scanner LS′ since the SOI substrate is expensive.